Thermorecording

ABSTRACT

A heat sensitive recording layer which is normally permeable by water and consists essentially of a hydrophilic binder having generally homogenously distributed therethrough finely divided particles of a hydrophilic thermoplastic polymer softening at at least about 10*C above room temperature and also containing therein finely divided dye or pigment capable of absorbing electromagnetic radiation and converting the same into heat, is exposed while in heat conductive contact with the radiation absorptive image markings of an original to be reproduced for a time not greater than 10 1 second to electromagnetic radiation of an intensity of at least 0.3 Watt. sec per sq.cm and sufficient to heat the areas of the layer corresponding to the non-image areas of the original to reduce the water permeability thereof; and is then treated with an aqueous liquid to develop the image therein by selective permeation by the aqueous liquid of the areas of unchanged permeability.

United States Patent Vrancken et a1.

[ THERMORECORDING [75] Inventors: Marcel Nicolas Vrancken, Hove,

Belgium; Wolfgang Liissig, Cologne-Sta'mmheim, Germany [73} Assignee: Gevaert-Agfa N.V., Mortsel,

Belgium Notice: The portion of the term of this patent subsequent to Nov. 4, 1986, has been disclaimed.

[22] Filed: May 17, 1 966 [21 Appl. No.: 550,834

30 Foreign Application Priority Data May 17, 1965 Great Britain 20818/65 May 29, 1965 Great Britain 21985/65 [52] US. Cl 96/36, 96/2, 96/11,

96/27 R, 96/28, 96/29 R, 96/29 D, 96/30, 96/31, 96/33, 96/36.2, 96/36.3, 96/36.4, 96/47, 101/457, lOl/458, 101/461, 101/459, 101/462, 101/463, 101/464, 101/467, 101/469, 101/470, 117/l.7, 1l7/3.5, 1l7/17.5, 117/356, 117/362, 117/36.7, 1l7/36.8, 117/369 1451 *Feb. 19, 1974 2,830,899 4/1958 Brownf... 96/36.3

3,476,937 11/1969 Yrancken 250/65 FOREIGN PATENTS 0R APPLICATIONS 950,870 2/1964 Great Britain 96/33 OTHER PUBLICATIONS Van Der Grinten Bulletin, Thermographic Writing and Copying Methods and Materials, Aug. 1, 1963, pp. 5-6

Murray, Theory and Practice of Reflex Copying, Aug. 1944, Photographic Journal, PP. 250-253 Primary Examiner-Roland E. Martin, Jr. Attorney, Agent, or Firm-William J. Daniel [57] ABSTRACT A heat sensitive recording layer which is normally permeable by water and consists essentially of a hydrophilic binder having generally homogenously distributed therethrough finely 'divided particles of a hydrophilic thermoplastic polymer softening at at least about 10C above room temperature and also containing therein finely divided 'dye or pigment capable of absorbing electromagnetic radiation and converting the same into heat, is exposed while in' heat conductive contact with the radiation absorptive image markings of an original to bereproduced for a time not greater than 10 second to electromagnetic radiation of an intensity of at least 0.3 Watt. sec per sq.cm and sufficient to heat the areas of the layer corresponding to the non-image areas of the original to reduce the water permeability thereof; and is then treated with an aqueous liquid to develop the image therein by selective permeation by the aqueous liquid of the areas of unchanged permeability.

11 Claims, 13 Drawing Figures FIG. 2

O O oo', ooO o. o o' 300 0 00' ,0. 00 :5.

I INVENTORS MARCEL NICOLAS VRANCKEN WOLFGANG LA'ss/e WATSON, COLE, GR/NDLE & WA TSON ATTORNEYS PAIENTEDFEBIQW K 3.793.025

SHEET 2 0F 7 INVENTORS MARCEL NICOLAS VRANCKEN WOLFGANG LANSSIG WATSON, COLE, GR/NDLE & WA TSQN ATTORNEYS PATENTED FEB I 9 {974 SHEET L W 7 mitt) V INVENTORS MARCEL NICOLAS VR'ANCKEN WOLFGANG LAss/e WA rso/v, COLE, GPINDLE & WATSON ATTORNEYS PATENTEDFEBIQW 3.793.025

' sum 5 0F 7 FIG. 70

FIG. 77

INVENTORS MARCEL NICOLAS VRANCKEN WOLFGANG LA'ss/o WATSON, COLE, GRINDLE & WA TSON ATTORNEYS PAIENIEDFEBIQIBH v V 3,793,025

sums o 7 INVENTORS MARCEL NICOLAS VRANCKEN WOLFGANG LA'SSQIG WATSON, COLE, GRINDLE & W4 TSON ATTORNEYS PATENTED 9W4 3. 793 O25 SHEEI71F7 FIG. 73

INVENTORS MARCEL NICOLAS VRANCKEN WOLFGANG LA 55/6 WATSOMCOLE, GR/NDLE 8 WATSON ATTORNEYS THERMORECORDING The present invention relates to a method for recording respectively reproducing information by means of electromagnetic radiation and a heat-sensitivematerial comprising at least one heat-sensitive element and substances wherein heat is produced by exposure to electromagnetic radiation.

In Belgian Patent Specification 656,713 it is disclosed that a heat-sensitive recording materialcomprising at least one sheet or layer containing thermoplastic polymer particles with or without continuous binder medium differing from. said particles in permeability and/or lyophobicity can be used. for recording a heat pattern as a permeable-impermeable and/or lyophiliclyophobic differentiation.

More particularly the recording method according to said Belgian Patent Specification comprises the steps of record-wise subjecting to the action. of heat a recording material comprising at least one layer or sheet having incorporated therein particles. composed wholly or mainly of ahydrophobic thermoplastic polymer, said layer or sheet either entirely or substantially. entirely consisting of said. particles or wholly or mainly. consisting of a. dispersion of said. particles in a hydrophilic binder in. aratio greater than. 1:15 by weight.

It is an object of the present invention.- toprovide a. method. for recording a pattern of electromagnetic ra diation in terms of a differentiation. in. permeability and/or lyophility. and/orsolubility and/or meltability.

It is more particularly an: object of the present inven tion' to providea method for recording; a. pattern: of visible light in terms of a differentiation in permeability and/or lyophility and/or solubility and/or meltability.

It is a further object of the present invention to provide different embodiments for producing printing masters, graphic printing master, a. letterpress or-gravure mas.- ter, a magnetic printing master, ahydrotype master and a hectographic printing master.

Yet another object of the present invention is to pro.- duce a visiblecopy of anoriginahwhich may. be a transparency or an. opaque original having light-reflecting areas by means of recording materials and; exposure techniques described herein.

These and other objects as well-'asadvantagesof this.

invention. willappear hereinafter and are: illustrated by means of drawings, which, however, should: not be considered as a restriction thereof. p

It has been found that these objects can be. accomplished by a method for recording respectively reproducing information which method comprises recordwise or information-wise exposing to electromagnetic radiation a recording material, which comprises at least one recording layer (which may be carried by a support or may be a self-supporting layer or sheet) incorporating one or more hydrophobic thermoplastic polymers in the form of particles, and wherein; said layer isprepared starting; from an: aqueous dispersion of said thermoplastic polymer particles, and. said particles in said material are in heat-conducting relationship with one or more substances, which. absorb electromagnetic radiation in atleast a part of the wavelength range of said radiation and convert the corresponding part of said radiation into heat, the-exposure being of high intensity and short duration 50- that an. image; or record is formed in or on said layer in terms of a difference in such. as a. screen-printing, master, at plano permeability, and/or lyophility and/or solubility and/or meltability.

Although the heat-sensitive layer for use according to the present invention need not contain a binder it preferably contains a hydrophilic binder but in a ratio smaller than 1:] by weight in respect of the thermoplastic particles. Best results are obtained with a recording layer containing one or more hydrophobic thermoplast-ic polymers in the form of particles dispersed in a hydrophilic binder in a ratio of 3:2 by weight.

According to a preferred embodiment the exposure is carried out by means of electromagnetic radiation the greater part of which (at least 70 percent of the irradiationenergy) is composed of electromagnetic radiation within a wavelength. range beneath 700 nm. According to the present invention. the exposure is preferably carried. out by means of visible light.

The short duration exposure of the recording layer preferably does not exceed 10 second, and according to a preferred practice the exposure of one and the same area of the recording layer takes less than 10 secondand ispreferably in a period of time comprised between. 10 and 10 second.

The process according tothe present invention depends for its result on a selective or differentialheating of the recording layer so that a property of the said.

layer,.e.g-. its meltability,water-permeability, solubility in water or an organic solvent, and/or hydrophility becomes selectively or differentially modified.

The imagedifferentiationis obtained by the heat prodiucedi in:the-said substances absorbing electromagnetic radiation. In order to transfer or conductthat heat to the thermoplastic polymer particles of the recording layersaid substances have to-standinheat-conducting relationship therewith and therefore are preferably present in the recording layer itself, although they may be present in another material or member located in intimate contact therewith.

The principle of recording according to the present invention. can be readily appreciated from a single example, viz. a recording layer composed of hydrophobic thermoplastic polymeric material in the form of particles applied from an aqueous dispersion whether or not containing a certain amount of hydrophilic binder so that theulayer is waterpermeable in view of the presence of intersticies between the said particles. lf lightabsorbing substances are present in the recording layer and are in. heat-conducting or heat-exchanging relationship with the polymer particles, and the system is exposed for a. very brief time to a pattern of highintensity' electromagnetic radiation, heat is generated in. the areas wherein the substances absorbing electromagnetic radiation are intensely irradiated and the cles must be present in a significant proportion in the recording layer.

The record in terms of hydrophility and/or permeability and/or solubility and/or meltability can be used in. many different ways as will. be illustrated hereafter. These-various modes of use include processing steps for making the record visible.

In itspreferred form the recording process according to the present invention can be defined in the steps of 1. providing a recording material, comprising at least one substantially dry and water-permeable layer containing particles composed wholly or mainly of a hydrophobic thermoplastic polymer disposed in a hydrophilic binder in a ratio greater than 1:1 by weight, said particles preferably softening between and 200C above room temperature and sizing preferably of from 0.01 p. to 50 p., and being in heat-conducting relationship with one or more substances which absorb visible light in the whole visible spectrum or in a part thereof and convert it into heat;

'2. record-wise flash-exposing the recording material to electromagnetic radiation containing a substantial amount of visible light so that the recording material undergoes a selective or differential de crease in permeability and/or lyophility and/or solubility and/ormeltability according to the light radiation record.

When referring to selective or differential decrease in permeability and/or lyophility and/or solubility and/or meltability according to the radiation record we mean that the achieved permeability or lyophility and/or solubility and/or meltability pattern constitutes a detect able record of the visible radiation pattern conveying the information to be recorded.

By record-wise or information-wise exposing to electromagn'etic radiation is meant that the exposure may be progressive (in the sense that the exposure of a recording tape to spoken information is progressive) or simultaneous, e.g. as is the case of reflectographic or transmission exposure respectively to or through an original, e.g., a printed text or silver image transparency. When assuming, for example, that the information to be recorded is in the form of written or printed matter, the record in terms of differential lyophobicity and/or permeability and/or solubility and/or meltability may be legible orlaterally reversed and may be developable as a record that is positive or negative with respect to the original.

From the statements that the differentiation consti-- tuting the record may be in terms of the degree of permeabilityand/or lyophobicity and/or solubility, and/or meltability, it will be understood that it is unnecessary for the recording sheet or layer, which is image-wise or record-wise heated according .to the method of the present invention, to exhibit some areas that are completely impermeable and/or lyophobic and/or insoluble and/or unmeltable and some areas that are completely permeable and/or lyophilic, and/or soluble and/or meltable. v The particular degree and/or kind or kinds of differentiation necessary in any given case will depend upon the intended use of the differentiation record, in other words, on the manner in which this record is to be read or developed. As will be apparent from the following description, the invention can be applied in a considerable variety of recording and copying techniques including, e.g., photographic recording and photographic and/or mechanical copying methods.

The process according to the invention is suitable for the preparation of prints by the reflex copying method or by usual transmission printing, i.e., direct exposure, e.g., in contact. When applying a reflex copying method, the intensity of exposure and the heat-' sensitivity of the recording layer are chosen in such a way, that on the absorption of the light rays directed to the original and striking undifferentially the lightsensitive layer, the heating resulting therefrom causes practically no or only'a slight loss of permeability and- '/or of lyophility and/or solubility and/or meltability of the heat-sensitive layer.

The additional image-wise heat resulting from the image-wise reflected light produces in the recording material the practical useful image differentiation between the areas struck by reflected light and those which are not struck thereby.

For reflex exposure the layer or layers of the recording material should obviously be sufficiently transparent. When applying the transmission printing process the recording material or any constituted layer thereof, if it comprises more than one layer, may be opaque.

The notion transparent pertains to the printing light used, which in the case of a gas discharge exposure device substantially consists of light with wavelengths ranging from 0.3 p. to l u According to the type of light source producing visible light a more or less great amount of infrared radiation and ultra-violet radiation can be present in the recording light.

For the conversion of visible light into heat finely divided black or dark coloured pigments or dyes are pref- 'erably worked up into the heat-sensitive layer and may be worked up in another layer or sheet adjacent thereto, provided a sufficient heat-conducting relationship between said substances and the thermoplastic polymer particles will exist. I

As to the mechanism of recording it is assumed without the intention of restricting the invention hereby, that the finely divided hydrophobic thermoplastic polymer particles, which are surrounded by a hydration layer or by means of a wetting agent are dispersed in a hydrophilic binder can enter into intimate contact with one another due to the locally very intense and sudden heating, thereby forming substantially impermeable polymer film or net-work of hydrophobic polymer particles sticking to one another. v

Having stated in general the concepts of this invention, a detailed description will now be made to the composition and structure of various heat-sensitive materials, the type of radiation source, and the exposure techniques used in the present invention.

FIGS. 1-8 are enlarged sectional views of seven types of heat-sensitive materials according to the present invention. v I

FIG. 9 diagrammatically illustrates a reflectographic flash-exposure method.

FIGS. '10, 12 and 13 are schematical drawings of recording elements in combination with an exposure device.

FIG 11 is a diagrammatic drawing of an apparatusused in a transfer process described further on.

As is illustrated in FIG. 1 a heat-sensitive material can contain a heat-sensitive layer 1, which is applied to a support 2 and which comprises dispersed particles of a hydrophobic thermoplastic polymer 3 and particles 4 of a substance or substances capable of absorbing electromagnetic radiation and converting it into heat in a continuous phase of hydrophilic binder 5.

FlG. 2 shows a recording material in the form of a self-supporting sheet 6, formed by a dispersion of particles 4 absorbing electromagnetic radiation and thermoplastic polymer particles 3 in a hydrophilic binder 5.

A heatsensitive matcrial can further contain, as is illustrated in FIG. 3, a heat-sensitive substantially dr'y porous coating 7 applied'to a support 2, said coating 7 essentially consisting of hydrophobic thermoplastic polymer particles 3 and particles 4 of a substance capable of absorbing electromagneticradiation and converting it into heat. The said coating 7 is preferably applied from an aqueous latex composition so that the polymer particles can be surrounded then by a hydration layer, which prevents the polymer particles from sticking but which can be destroyed by heat.

A heat-sensitive material can further contain, as is illustrated in FIG. 4, a heat-sensitive layer 1, a support 2, and an intermediate layer 8 containing dispersed particles 4 of a substance capable of absorbing electromagnetic radiation and converting it into heat.

A heat-sensitive material can further contain, as .is illustrated in FIG. 5, a top layer 9 containing dispersed particles 4 of a substance capable of absorbing electromagnetic radiation and converting it into heat and adjacent thereto a heat-sensitive layer 1 applied to a support 2.

The heat-sensitive material can further contain, as is illustrated in FIG. 6, a heat-sensitive layer 1, a support 2, an intermediate layer 8, and a top layer 9, both last mentioned layers containing dispersed particles 4 of a substance capable of absorbing electromagnetic radiation and converting it into heat.

It will be apparent that in materials like those represented by FIGS. 4 to 6 wherein the electromagnetic radiation absorbing substance (whether in the form of particles or otherwise) is present in a layer other than the recording layer, the layer in which said electromagnetic radiation absorbing substance is present must not be so heat-conductive that the heat given off by said substance under intense irradiation with said radiation is dissipated alongg the layer. On the other hand the conduction of heat from the substance to the polymer particles must not be prevented. These factors must be taken into account in selecting the composition of the layer containing the electromagnetic radiation absorbing substances and the thickness of this layer.

The heat-sensitive material can further contain, as is illustrated in FIG. 7, a heat-sensitive layer 1 applied to a support 2 said heat-sensitive layer containing in a hydrophilic binder 5 hydrophobic thermoplastic polymer particles 3, which contain dispersed'particle s 4 of a substance capable of absorbing electromagnetic radiation and converting it into heat.

The heat-sensitive material. can also comprise a support which is impregnated with the heat-sensitive coating composition. Examples of suchsupports are those suitable for use in stencil preparation, e.g., Japan paper. v

So far reference has been more particularly made to the use of the electromagnetic radiation absorbing substance in finely divided form,(disperscd state).- but his to be understood that ,a said radiation absorbing substance may be in some other form, e.g., it may the present in dissolved state or may itself form a continuous phase or layer.

As already mentioned the heat-sensitive layers or self-supporting sheets for use according to the present invention may contain some amount of hydrophilic binding agent. Suitable hydrophilic binding agents are, e.g., hydrophilic natural colloids, modified hydrophilic. natural colloids, or synthetic hydrophilic polymers.

More particularly they may. be selected of watersoluble natural or modified natural hydrophilic colloids, as e.g. gelatin, glue, casein, zein, hydroxyethylcell'ulose, carboxymethylcellulose, methylcellulose, carboxymethylhydroxyethylcellulose, hydroxyethylstarch, gum arabic, sucrose.octaacetate, ammonium alginate, sodium alginate and hydrophilic derivatives of such colloids. They may also be selected of such synthetic hydrophilic polymers as, e.g., polyvinyl alcohol, polyvinylpyrrolidone, polyvinylamine, polyethylene oxide, polystyrene sulphonic acid, polyacrylic acid and hydrophilic copolyr ners and derivatives of such polymers.

Some of these polymers and derivatives thereof are soluble in water containing some alkali or acid.

The hydrophilic film-forming material used for the manufacture of a heat-sensitive recording layer or selfsustaining sheet according to the present invention may be hardened for obtaining a higher mechanical strength. Thus, a film-forming binding agent of the gelatin type may be hardened by reaction with an aldehyde such as formaldehyde or glyoxal. Also suited therefor are alum and hardening agents incorporated directly together with the colloid as an ingredient in the coating composition or applied afterwards by treating the layer or recording sheet with a solution thereof.

Application of the hardening agents as ingredients in the recording layer or sheet composition containing a hydrophilic binder is generally chosen as a function, of the desired mechanical strength. The amount of hardening agent may range from 0.5 to 5 percent by weight. The treatment of the recording layer or self-sustaining sheet may be carried out with a solution having a concentration of 2 to 25 percent by weight of the hardening agent.

For the purpose of a wet or dry transfer of portions of the recording layer that were not image-wise exposed onto a receiving material, the hydrophilic binder preferably contains a softeningagent. Suitable softening agents for gelatin are urea and potassium thiocyanate. Other suitable softening agents for gelatin are described in J. Phys. Chem. 60 (1956) 1,299-1,306. In

the case a wet transfer is applied the softening agent may be present in the moistening liquid in order to improve the transfer of unexposed portions of the recording layer by pressing it on a receiving material.

The hydrophobic thermoplastic polymer, which is the most important heat-sensitive'substance of a recording element used according to the present invention, has to form a porous layer or water-permable layer when coated from an aqueous dispersion at a temperature not substantially higher than room temperature and dried. The polymer particles preferably soften between 10 and 200C above room temperature. As examples of suited polymers may be cited polymers having a melting point or a glass-transition temperature between 10 and 200C above room temperature. More particularly are suited, e.g., poly(ethylene) and poly(- vinylidene chloride)*having a melting point of 1 10 and 190C. respectively, and the following polymers with their respective glass-transition temperatures poly(- styrene)(100C), poly(methyl methacrylate)(comprised between and 105C), poly(ethyl metha cry1ate)(50C), poly(vinyl chloride)(near 70C), poly(acrylonitri1e)(near C), poly(N-vinyl carbazole) (200C).

idized polyethylene.

, As is-known, the glass-transition temperature can be lowered by the addition of some substances called plasticizers. More particulars about suited plasticizers and the glass-transition temperature of homoand co-;

polymers can befound e.g.', iri Georges Champetier,

. Chimie Ma'cromoleculaire Generalites, Librairie Armand Colin Paris Verne, p. 194-198. It appears therefrom that by copolymerisation or copoly-condensation system, a surfactant and a water-soluble catalyst, e.g.,

hydrogen peroxide or a persulphate. The polymer is obt ained as a stable dispersion of polymer particles in waa scale of glass-transition temperatures can be obtained according to the ratio of the monomer or. condensation reagents used in the copolymerisation and copolycondensation respectively. The molecular weight of the polymers usable in thepro cess according to the present invention may vary withinwide limits. Polymers possessing a molecular weight ranging from 5,000 to 1,000,000 are preferred. Poly(ethylene) possessing a molecular weight of 15,000 to 50,000 appeared to be very suited; Although there is some relationship between the melting point or glass-transitiontemperature ter.

v Thepolymer particles in dispersion may size from 0.01 p. to 50 t. However, the larger the particles, the

less the resolving power on recording. Very good results are obtained with dispersions-the dispersed polymer particles of which size from 0.05 a to 2 it;

Dispersions wherein the dispersed particles size from 1 p. to 1 mp. are considered as colloidal systems. A.colloi- 'dal system the continuous'phase of which is formed by water- (dispersingmedium) and the'dispersed phase is formed by particles sizing from 1 to 0.001 n is called a hydrosol. Good results are obtained when using such hydrosols the polymer particles of ,which are not greater than 0.1 p.. Goodresults are further obtained when using in the recording layer amounts by weight of thermoplastic polymer particles comprised between 0.5 g and 10 g/sq.m. The thickness of recording layers used in the present invention preferably varies between 0.5 p. and 10 ,u.. 3 v i I As was stated hereinbefore the heat-sensitive layer according to the inventionneed-not contain a'bincler.

hydrophilic binding agent. The aqueous dispersion of the homopolymer or copolymer isprepared preferably by radical polymerisation in',ernulsion of one or more polymerisable monomers according to: known tech-,

- n'iques', e.g'.', those described by W. Sb'renson and T.W. Campbell, Preparative Methods of Polymer Chemistry,

lnterscience Publishers, New York (1961). In this radical'polymerisation use is made of dispersing agents such as'thosede'scribed by K. Laux, DieGrenzflachenaktiven Stoffe in Winnacker-Kiichlers Chemische Technologie Carl Hasen Verlag, Munich (1960) p. 155-242.

Aqueous dispersion of polymers prepared by dispersing'a solution of a water-insoluble polymer in a waterimmisciblesol-vent in an aqueous solution of a hydrophilic binding agent are also considered; As solvents may be mentioned, e.g., chlorinated hydrocarbons,

such as methylene chloride and trichloroethylene.

According to another technique aqueous polymer dispersions can be obtained by dispersing a molten thermoplastic polymer in water in the presence of wettingagents. In order to improve the dispensing properties the polymers may have in their structure a certain amount of hydrophilic groups as is the case in partly oxwhich are appropriate Further, polymer dispersions,

The'sup port and/or the-drying technique of the layer may be chosen such that a natural adhesion occurs be tween the layer free from binding agent and the support. A slight sticking, e.g., by heating, of the polymer particles to one another and to the support without serious harm to the porosity .of the layer'enhances the mechanical strength thereof. Since a binder is not strictly necessary, the amount of hydrophilic binder in recording elements accordingtathe present invention can vary between Opercent and a relatively high percentage The amount of hydrophilic binder is mainly deters mined by the required hydrophilic-hydrophobic differentiation obtained by the image-wise heat treatment of the heat-sensitive layer. In general, however, a weight ratio of 1:1 of hydrophilic binder to hydrophobic thermoplastic particles is too high. On the other hand with a ratio of 3 parts by weight of hydrophobic thermoplastic particles to 2 parts by weightofhydrophilic binder a very marked image-wise change from hydrophilic to 'hydrophobic' and from permeable to impermeable,

which is suited for the production-of copies as well as for reproduction purposes,- is obtained.

The temperature at which the heat-sensitive element undergoesa substantial loss in permeability is'preferably in the range of 40-200C.

It is evident that the heat-sensitive'material, before or during the creation .of the image-wise differentiation,

can be integrally heated to a certain temperature below the temperature of image formation of the heatsensitive material. By such means the amountby which the temperature of the thermoplastic particles has to be for'applicatio n inthe present invention can be obtained by dispersing in water mechanically finely divided poly-' mer particlespreferably with the help of surfactants and/or hydrophilic protective colloids such as poly(vinyl alcohol) and gelatin. Latices obtained by emulsion polymerisation are preferred. In this polymerisation technique the monomer is dispersed by stirring to very fine droplets in the presence ofwater, emulsifiers (soaps, ammonium oleate, sulphonated fatty alcohols and'the like), protective colloids (carboxymethylcellulose, poly vinyl alcohol) andthe like), a buffering raised in local areas by heat conduction from or heat exchange with the light-absorbing substance consequent upon its image-wise exposure to light is correspondingly reduced. v

Pigments suited for use according to the present invention and which convert visible light into heat, are, e.g., carbon black, graphite, oxides orv sulphides of heavy metals, particularly of those-heavy metals having an atomic weight between 45 and 210, such as manganese or lead sulphide or these heavy metals themselves in finely divided state such as silver, bismuth, lead, iron,

cobalt, or nickel. At present, preference is for carbon black as light-absorbing material in carrying out the invcntion.

Further suitable radiation-absorbing pigments and other data relating to radiation-absorbing substances are disclosed in the specification accompanying Belgian Patent Specification No. 657,502. This specification should accordingly be read in conjunction herewith and be deemed to form part of the present disclosure.

According to a special modification of the recording element the hydrophobicthermoplastic polymer particles themselves may contain the substances absorbing visible light and converting it-into heat. Such polymer particles can, e.g., be prepared by carrying out the emulsion polymerisation reaction in thepresence of such substances dispersed in the reaction medium.

As an example of an intimate mixture of dispersed pigment and polymer particles the following preparation of the dispersion of polyethylene and carbon black is given.

40 g of a partly oxidized polyethylene, prepared according to U.K.Patent specification No. 997,135 by the oxidation of polyethylene and having an average molecular weight of 7,000, a crystalline melting point of 130C, and an acid number of 26-30 are melted between 130 and 150C. To the molten polyethylene are added 2.2 ccs of 50 percent aqueous potassium hydroxide, 18 g of n-hexadecyloxy-decaoxyethylene, and then portionwise whilst stirring 20 g of carbon black having a particle size of about 0.04 a. A viscous black paste is obtained, which is allowed to cool to room temperaa thennometer, a manometer, and a stirrer are placed 60 g of the above finely ground black polymer mixture and 300 ccs of demineralized water. The dispersion obtained is heated to 90C whilst stirring, whereupon the autoclave is sealed. Stirring is accelerated to 2,000 rpm, while the temperature is raised to 150C. After 30 minutes the autoclave is allowed to cool to room temperature. A homogeneous black dispersion is obtained of pH 8.3.

According to another modification a certain amount, taking into account the degree of required transparency of the recording material, or all of the hydrophobic thermoplastic polymer particles may contain in dissolved'state a substance transforming electromagnetic radiation into heat, so that the transparency and heatsensitivity of the recording element can be modulated by the polymer particles themselves.

The heat-sensitive layer may comprise from 0.01 to 1, preferably from 0.1 to 0.5 percent by weight of pigment calculated on the total weight of the layer. Black or deep black coloured pigments are preferred when no colours have to be reproduced. Particularly in the case of reflex printing, the optical density of the light absorbing layer (grey layer) should preferably be between 0.25 and 0.78.

For the recording of coloured originals the coloured substance or mixutre of such substances absorbing only light of a part of the visible spectrum and converting that light into heat are preferably absorbing light of one of the primary colours (red, green, blue) or subtractive colours (cyan, magenta, yellow).

Substances which absorb visible light of a part of the visible spectrum and wherein absorbed light energy is transferred into heat are e.g. dyes belonging to the classes of the azo-, triarylmethane-, xanthene-, acridine-, methine-, azine-, phtha1ocyanine-, anthraquinone and allied dyes. I

Said substances can be used in dispersed and/or dissolved state, and when used in dispersed form preferably in a grain size lower than 0.1 p.

The amount of said substances in a heat-sensitive element depends on the required heatsensitivity of such an element, the intensity of the irradiation to be employed and the required yield of heat resulting from the irradiation of said substances.

When incorporated in the heat-sensitive material, said coloured substances are preferably used in the heat-sensitive layer itself in such an amount that an optical density of between 0.3 and 5 is obtained.

Coating of a heat-sensitive layer may be accomplished by conventional means such as by a roller coater, brush coater, spraying device, knife coater or by the use of an air-blade to control the thickness and distribution of the coating composition.

In a recording material comprising a recording or heat-sensitive layer on a support, the support of the recording layer may, according to the purpose of the material, be a rigid or a flexible member. The support may be permeable or impermeable, e.g., it may be waterpermeable such as a transparent web or textile. When flexibility is unimportant, plates of metal, glass or plastics, fiber board, cardboard or the like may be used.

According to their purpose the materials comprising a heat-sensitive element according to this invention may be built up differently. By way of example the heat-sensitive layer (whether or not comprising a hydrophilic binder) can be applied to a hydrophilic layer, which latter may be serve as a support. By hydrophilic layer a layer is understood that is wettable by water or by aqueous solutions. This layer may be porous or water-permeable. By way of example this hydrophilic layer may be composed mainly of natural or synthetic hydrophilic colloids. Examples of such layers are a gel-, atin layer, a light-sensitive silver halide emulsion layer, a water-permeable nuclei-containing colloid layer for application of the silver complex diffusion transfer process, a colloid layer containing pigments or dissolved dyes, or containing reaction components capable of producing a colour reaction, a hydrophilic colloid layer containing developing substances for silver halide or complexed silver halide, or a hydrophilic colloid layer containing finely divided metal that can be etched away, e.g., silver.

In addition to a hydrophilic binder occasionally present in the heat-sensitive layer, said layer itself may contain all kinds of ingredients such as electro-conductive particles, e.g., carbon black, and dyes that can be bleached, distilled, or sublimed, reaction components for the formation of dyes, catalysts for colour reactions, developing nuclei, light-sensitive substances, developing substances for silver halide or complexed silver halide, finely divided metal that can be etched away, reaction components that canbe distilled preferably below C, and other image-forming material. Further, this layer may comprise hardening agents for the hydrophilic binder and occasionally curing agents, which harden the hydrophobic thermoplastic polymer at elevated temperatures.

In the case of the application of a reflectographic exv posure the concentration of said ingredients, however, may not be so high that the heat-sensitive layer becomes too opaque.

The heat-sensitive layer occasionally comprising a hydrophilic binding agentcan also be applied to a hydrophobic layer, which may or may not serve as a support. By hydrophobic layer a layer is understood that is not or almost not wettable by water.

Such layers or supports are made, e.g., of cellulose ester derivatives, polyesters, polystyrene, glass and the like.

Further, the heat-sensitive layer used in the present invention can be applied between two hydrophilic layers, two hydrophobic layers, a hydrophilic and a hydrophobic layer, between two permeable layers, two impermeable layers, or between a permeable and an impermeable layer.

A layer or sheet being in contact or water-permeable relationship with the heat-sensitive sheet or layer may contain ingredients that can be of practical interest to produce a visible image in accordance with the recorded heat image, e.g., pigments, dyes, reaction components for the formation of dyes, developing substances, reaction components, or dyes that can be distilled or sublimed preferably below 80C, developing nuclei suited for use in the silver halide diffusion transfer process, catalysts for colour reactions, conductive particles and light-sensitive substances.

The effectiveness of the recording with electromagnetic radiation to be converted in heat depends in substance on the intensity of the radiant energy. For example, a recording element, which does not provide a sufficient physical differentiation in meltability, permeability, solubility and/or lyophility in the recording element with a particular source of energy, may be found fully effective if the energy level is substantially increased. With increased energy the distance between radiation source and recording element may be increased. Radiant energy absorbed in the absorbent printed areas of certainoriginals and converted to heat energy is more rapidly dissipated and prevented from affecting the contacting image-forming element when the radiant energy is of short duration and of a suitable high intensity. Lamp structures and systems capable of I providing such increased intensity are available and form no part of the present invention.

Light sources with a high radiation intensity and relatively short exposure time are the so-called flash lamps and more particularly the gas discharge flash lamps. According to the present invention good results are obtained with a xenon gas discharge lamp, which can supply an energy of 300-1000 Watt.sec. in a period 10 to l0 seconds.

According to a preferred embodiment of the invention such a gas discharge lamp, which is in the form of a thin tube, is fitted in a hollow glass cylinder (see FIG. 9) in order to make possible a uniform exposure of the recording material applied to the periphery of the cylinder.

More details about such a gas discharge lamp for use in carrying out the invention are given in the specification filed in German application No. A46 2l8, which specification should also be read in conjunction herewith and be deemed to form part of the present disclosure. 1

Evidently gas discharge lamps with a lower energy output can be used if the emitted energy is'focused onto a relatively small heat-sensitive area. So, e.g., a gas discharge lamp with an energy output of 40 Watt.- sec. is suited for copying 6 X 6 cm and 6 X 9 cm originals on heat-sensitive materials as described in the present invention. For materials having an optical density of at least 1 resulting .from the presence in the recording layer of light absorbing substances a light energy of 0.3 Watt. sec. per sq.cm will in practice suffice for the desired image differentiation. It is further'selfi explanatory'that exposure may be progressive and intermittent. In other words the'heat-sensitive material may be scanned with an image-wise modulated lightspot of high intensity, eg, a laser beam, or may be progressively exposed through a slit wherein, e.g,, copying light of a continuously emitting tubelike radiation source is focused.

A great advantage of the thermo-copying process according to the present invention in comparison with the classical thermographic copying processes lies in the high sensitivity, the sharpness of the obtained images and the possibility to use visible light, which enables one to reproduce originals containing image-markings, which are not infra-red absorbing nor heat-conductive.

During the exposure through an original (transmission printing) the original is placed between the radiation source and the recording material. According to a first combination the heat-sensitive layer can be placed in contact with the original, occasionally by using a transparent inter-sheet or inter-layer. In this combination the support of the recording elemen't can be opaque or transparent. According to another combination the recording material can be placed with its back-side (support), which in that case preferably is side an element reflecting said radiation.

Before giving some examples for practising recording and reproduction of the present invention, a short survey is given of different systems, which are suited for the manufacture of copies and masters for the reproduction of originals starting from a heat-recording material according to the present invention. This survey is intended for illustrating the possibilities and advantages of the invention without limiting therefore the scope of this invention. I

According to a first system, the image-wise differentiation in permeability and hydrophility obtained by exposure is utilised for applying by image-wise diffusion image-forming substance or substances in the recording element by a liquid treatment or transferring such substances from the recording element to a receiving material respectively, said image-wise diffusion being possibleas a consequence of this differentiation. By way of example for the. first embodiment said imaged recording material is dipped into an aqueous dye solution, so that the dye can diffuse in the recording ele- According to another embodiment the recording material, e.g., as a self-sustaining sheet, after exposure can lution of a catalyst for initiating a colour reaction between components in the recording material or a solution of a colourless reaction component capable of giving a colour reaction with a colourless or slightly coloured reaction component in the recording material can be used instead of a dye solution. 7

By way of example for the second embodiment it is possible to incorporate into the recording element coloured substances that can be bleached out and which are bleached by a bleaching agent diffused in the areas of the recording material that remained permeable. According to an alternative of thatembodiment, a conductive substance, e.g., a metal that can be etched away, such as colloidal silver, and that is homogeneously dispersed in the recording element, is imagewise etched away by the etching liquid diffusing into the permeable areas. The heat-sensitive layer can be applied to an etchable base material, e.g., a zinc or copper plate. When using this material it is possible to produce a lettertype or intaglio printing master by etching.

In a second embodiment of image-formation wherein diffusion is applied, the image-forming substance incorporated in the recording material is transferred by diffusion from the areas that remained permeable toan image-receiving material. So, it is possible, e.g., to incorporate a soluble dye into the recording element or into a layer being in a liquid-permeable relationship therewith, said dye being capable of diffusing therefrom image-wise to a receiving material when the heatrecording element is wetted.

According to an interesting technique the heatsensitive layer or adjacent as well as subjacent layer comprises a liquid or solid substances, e.g. dyes, in incapsulated form. After image-wise impermeabilisation of the heat-sensitive layer pressure is exerted on the surface of the recording material. As a result of this pressure the capsules burst so that the contents are at disposal at those areas of the heat-sensitive layer that remained permeable.

Through these areas having remained permeable contents of the capsules can be transferred, e.g., to a receiving material (recording process requiring no processing liquid or bath). The preparation of suitable capsules is described i.a. in the United Kingdom Patent Applications Nos. 6860/63, 27,401/63, 27,402/63, and 27,403/63.

Instead of a dye, a colourless reaction component or catalyst, whether or not in incapsulated form, for bringing about a colour reaction with a reaction component in the receiving material can obviously be incorporated in the recording element.

It is also possible among others to incorporate into the recording material silver salts, which can be complexed and which in their dissolved form can diffuse to a receiving material containing reduction nuclei or development nuclei, whereupon according to the areas of the recording material that remained permeable, silver is deposited image-wise.

In these diffusion methods the image-forming substances such as a dye, a metal that can be etched away, or reaction components need not be present in the recording element itself. They can also be incorporated into a layer or support being in-permeable relationship therewith.

form an image-wise water-permeable membrane through which, by way of example, an aqueous dye solution can diffuse continuously. In this way a hydrotype master is obtained by means of which several copies of the original can be printed on transfer material.

Said membrane can also be used for electrolytic printing since the said membrane being in close surface contact with a receiving material as an electrode only transmits electrolyte through the permeable portions with the result that an image-wise electrolytic deposit of image substance is formed on said electrode mate- 'rial.

According to a second system the areas of the heatrecording material that remained permeable and soluble are eliminated, e.g., by washing out or degrading of the hydrophilic binder. In that case the recording element may comprise a dye, e.g., a (coloured) pigment or a dissolved dyestuff so that on eliminating by liquid the image areas that remained permeable, a copy of the original is obtained.

By applying said second system a gravure master can be produced starting from a heat-imaged recording layer, which is applied to a metal support that can be etched. After elimination of the portions of the recording layer that remained permeable and hydrophilic, e.g., by washing out, the uncovered metal can be etched away image-wise. In this way, e.g., printed circuits can be produced. After the elimination, e.g. by means of an organic solvent, of the residual portions of the recording layer, the etched metal plate is ready for being used as a gravure master.

By applying said second system, a letterpress master can be manufactured by merely washing away the portions of the heat-imaged recording layer that remained permeable and hydrophilic, said washing process being followed, if needed, by the hardening of the impermeabilised portions of the recording layer. In this way the impermeabilised portions form a relief image.

When the recording layer is applied to a strongly conductive support, e.g., of aluminium, an electrostatic printing plate can be made of this material after heatimaging. By washing away the permeable portions of the recording layer according to the present invention containing, e.g., a hydrophilic binder, the conductive material is uncovered image-wise. The portions of the recording layer that were made impermeable possess a considerably higher electric resistivity than the strongly conductive support. By this difference of electric resistivity and by the insulating character of the remaining polymer portions, an electrostatic'charge pattern can be formed in accordance with said polymer portions by electrostatically charging. These portions can either be developed in a known way, e.g., by means of powder, or be utilised for the image-wise transfer of electric charges to an insulating transfer sheet. Alternatively, the so-treated recording material can be used as an electrostatic printing form or as a material containing a permanent conductivity image. Such material and the use thereof are described in the United Kingdom Patent Specifications 964,872 and 983,841.

By applying said second system also a stencil or screen-printing master can be manufactured starting from a heat-imaged recording material according to the invention. For this technique one or both sides of a screening material are coated with a recording layer or the screening material makes part of a self-sustaining sheet as described hereinbefore. As screening material material to be printed conformably to these areas. The

image-wise open areas are obtained according to the present invention by washing out or etching away the recording layercomposition except for the screening material at the areas where this layer or sheet remained permeable and hydrophilic.

According to a third system the image areas that remained permeable and hydrophilic are transferred to a receiving material in wet and/or heated state by squeegeeing and tearing out.

This type of transfer is possible if the cohesion of the ened polymer to a receiving material by pressing the heat-sensitive layer of the exposed recording material against a receiving material, e.g., paper, while heating, e.g., between two heated rollers, and finally by separating both materials. (Recording process without processing liquid).

The composition of a recording material suited for use in this process is illustrated in FIG. 8. This recording material comprises a heat-sensitive layer 1, which is applied to a polymer layer having a softening point below the temperature at which the heat-sensitive layer is impermeabilised. The polymer layer is applied to a support 2. The heat-sensitive layer contains dispersed particles of a hydrophobic thermoplastic polymer 3 and particles 4 of a substance or substances capable of absorbing visible light and converting it into heat in a continuous phase of hydrophilic binder 5.

matter of the receiving material is stronger than that of 20 the matter in the permeableareas of the recording layer and if the adhesion between said permeable areas:

and the receiving material is stronger than the cohesion of the matter of said permeable areas.

- This transfer successfully occurs when separating after pressing together a wetted'image-wise exposed recording material from a receiving material preferably having a hydrophilic and/or porous surface. In that case the recording material preferably comprises either a recording layer containing a hydrophilic binder wherein the hydrophobic thermoplastic polymer particles are dispersed or a recording layer built up by a porous coating of the said polymer particles applied to a hydrophilic, preferably a colloid layer capable of swelling considerably.

The contrary type of transfer is possible if the cohesion of the substance in the contacting material, called in that case transfer material, is less than that of the substance inthe permeable areas of the recording layer and if the adhesion between said permeable areas and the transfer material is stronger than that of the substance of said transfer material. For example a dye layer of a carbon paper having a scarcely hydrophobic surface such as is used in the process according to the United Kingdom Patent Specification 996,963, after being pressed onto the moistened image-wise exposed recording layer, can be transferred image-wise to the permeable and hydrophilic areas of the recording material on separating it therefrom. Before pressing the recording material onto a dye layer the hydrophilic binder of said material can be swollen so that a relief image is formed that makes possible a closer contact with the dye layer.

According to this third system it is thus possible to manufacture hectographic masters since the torn out material can contain a hectographic dye that is soluble in a spirit duplicating liquid or can contain a reaction component capable of forming'a dye with a reaction perature at which the heat-sensitive recording element becomes less permeable, and which is located beneath the recording layer to transfer the unexposed areas of the heat-sensitive layer together with a stratum of soft- According to a fourth system it is possible by the use of a low melting substance, e.g., a dye, in the recording layer itself, to transfer this dye by melting the recording layer in contact with a transfer material.

According to a fifth system the exposed recording material comprising an image-wise hydrophilichydrophobic differentiation is used for planographic printing either with a fat printing 'ink using in that case a damping system or with an ink consisting of a mixture of a coloured aqueous phase and a colourless or almost colourless oleophilic phase as described in the United Kingdom Patent Application 7800/65 which should be read in conjunction herewith.

Multicolour images can be produced byusing a heatsensitive material according to the present invention and containing more than one heat-sensitive element. So, it is possible, e.g., to record at least two of the colours used for subtractive colour mixture of a multicolour original in terms of a differentiation in permeability and/or lyophility in one material by using a recording material of the type described above containing a transparent support having at one side thereof a heat-sensitive layer containing, e.g., a red dye and at the other side a heat-sensitive layer containing a green dye or blue dye.

Multicolour printing is also possible. For that purpose three heat-sensitive materials are preferably used containing a heat-producing substance absorbing light in the red, the green and blue region of the spectrum respectively, i.e., materials containing acyan substance, a magenta substance and a yellow substance respectively.

The heat-sensitive material'containing the cyan substance and which is sensitive to red light, by the heat produced therein is made impermeable and hydrophobic in the areas corresponding with the red areas of the original.

The heat-sensitive material containing the magenta substance and which is sensitive to green light, by the heat produced therein is made impermeable and hydrophobic in the areas corresponding with the green areas of the original.

The heat-sensitive material containing the yellow substance and which is sensitive to blue light, by the heatproduced therein is made impermeable and hydrophobic in the areas corresponding with the blue areas of the original.

' Multicolour prints can be produced by using the obtained masters to print in register.

According to the printing system applied'hydrotype (aqueous ink see, e.g., United Kingdom Patent Application 7800/65 or offset-printing (lipophilic ink) inks having the colours used for subtractive colour mixtures (cyan, magenta, yellow) or inks having the colours used for additive colour mixtures (red, green, blue) are used. a i

For reproducing originals which contains separate markings in the pure primary colours blue, green and red, e.g., a letter heading containing blue, green and red letters, three separate heat-sensitive materials are used, which are sensitised for yellow, magenta and cyan respectively. by a blue, green and red dye or pigment being uniformly distributed in the heat-sensitive layer at the time of the exposure to white light.

The following examples illustrate the invention.

EXAMPLE I To a cellulose triacetate sheet provided with a gelatin subbing layer alayer is applied pro rata of 12.5 sq.m. per kg from the following solution:

6 aqueous gelatin 650 ccs S aqueous pyrogallol I ccs l l aqueous saponin 20 ccs water to 1000 ccs On drying, a heat-sensitive layer is coated thereon pro rata of sq.m. per kg from the following coating composition:

50 aqueous carbon dispersion 3 aqueous gelatin 400 ccs 40 aqueous emulsion of polyethylene having 160 ccs a particle size of less than 0.1 p. and an average molecular weight comprised between 15,000

and 30,000

3 aqueous solution of the condensation I40 ccs product of oleic'acid and methyltaurine tion-reflecting background 23, the heat-sensitive layer 20 facing the original.

In this way the copying material l 9 consisting of the cellulose triacetate support 27, the gelatin prelayer 28 and heat-sensitive layer 20 is pressed against a glass cylinder 24 having a diameter of 8 cm. In the axis of this cylinder a xenon'gas discharge lamp 25 is placed, which on discharge between the electrodes 26 produces a radiation energy of 610 watt.sec. in 1/2000 sec. at 4 cm of the original. This radiation mainly consists of visible light. After exposure, the heat-sensitive m t 9 .LSP d a d at qatin m xiizein it in water for sec. and, after having removed mesh? plus water, by pressing it against a receiving paper containing iron(lll) chloride. This receiving paper was prepared by dipping common writing paper into I percent aqueous ironflll) chloride and drying. According tained by wetting the master again-after each contact with a sheet of receiving paper.

EXAMPLE 2 A poly(ethylene tcrephthalate) support of 0.1 mm thickness provided with a subbing layer for gelatin is coated with the following solution pro rata of 50 g/sq.m.:

l0 aqueous gelatin 935 g l0 aqueous saponin 30 g 3 aqueous HOSTAPON T (registered trade 7 30 g mark) 4 aqueous formaldehyde 5 g After solidifying, a heat-sensitive layer is applied thereto from the following composition pro rata of 36 g/sq.m.:

l0 '7 aqueous gelatin 100 g 40 aqueous dispersion of polyethylene [60 g having a particle size of less than 0.l p. and an average molecular weight comprised between l5,000 and 30,000

aqueous carbon dispersion containing pro 100 8 g g 53 g of carbon, 23 g of water, 18 g of glycol and 6 g of nonylphenylpolyethylene oxide 5 aqueous solution of TERGITOL 4' g (register trade-mark) 4% aqueous formaldehyde 5 g water 640 g After drying, the heat-sensitive copying material 30 (FIG. 10) obtained comprising a p0ly(ethylene terephthalate) support 31, a gelatin interlayer 32 and a heat-sensitive layer 33 is exposed together with an original 34 to be reproduced, as schematically illustrated in FIG. 10, with a xenon gas discharge lamp 35 irradiating the thermosensitiv'e material with an energy of 0.8 Watt.sec./sq.cm.

The exposed material is braced on the printing cylinder of a planographic printing apparatus and inked thereon with an ink of the following composition:

aqueous carbon dispersion containing 53 g of 100 g carbon, 23 g of water, 18 g of glycol, and 6 g of nonylphenylpolyethylene oxide 80 aqueous solution of a partly etherified 20 ccs melamineformaldehyde resin copoly(vinyl acetate/ammonium crotonate) 27 g (/5) l,S-hexanediol 27 g IO N ammonium hydroxide 2 g urea 6.5 g

53 aqueous dispersion of copoly(butyl l3 g acrylatc/vinyl acetate (50/50) white spirit (boiling range: l80-200C) 80 g xylene ,8-

Only the areas corresponding with the image areas of the original are wetted with the aqueous coloured phase of the ink. By means of the planographic printing machine and the regular supply to the copying material of said ink, black prints are obtained from the original on common paper acting as a receiving material.

The same results are obtained when in the composition of the heat-sensitive layer the amount of 8 g of said carbon dispersion is replaced by 30 ccs of a 10 percent aqueous dispersion of finely divided silver.

EXAMPLE 3 A material as described in Example .2, after being exposed as described in Example 2, is'slightly wetted with 'water and then with its heat-sensitive layer pressed against a receiving paper 36. The material and the receiving paper are led between two pressure rollers 37 and 38 (FlG. 11) at a travelling speed of about 10 cm/sec., the latter roller being heated to 35C. On emerging from between the rollers, both materials are immediately peeled apart. A thin stratum of the heatsensitive layer is transferred image-wise to the receiving paper so as to form a legible print in accordance with the original.

EXAMPLE 4 After being exposed as described in Example 2, the material as described in Example 2 is slightly wetted and pressed against the dyestuff layer of a hectographic carbon carrying no hydrophobic surface layer. After a contact time of about 1 min. both layers are separated. At the areas corresponding with the image areas of the original part of the dyestuff layer is transferred, so that a dyestuff-containing laterally reversed image of the original is obtained. This material can then be utilised as spirit duplicating master.

EXAMPLE A Japan paper weighing 14 g/sq.m. is dipped in a solution consisting of:

aqueous gelatin 200 g 40 dispersion of polyethylene as described in 200 g example 2 water 400 g carbon dispersion as described in example 2 2.5 g

5 aqueous solution of sodium tetradecyl 40 g sulphate When dried, this coated Japan paper possesses a weight of g/sq.m. The treated paper is exposed to i an electronic flashlight unit in the same way as described in Example 2. Subsequently, the material is dipped in a 5 percent aqueous solution of sodium salic'ylate and the areas corresponding .with the image areas of the original are washed away.

-Continued sulphate 5 aqueous solution of sodium tetradecyl g Subsequently, the material is dipped in a conventional bleaching bath. Only in the areas corresponding withthe opaque parts of the negative silver is bleached out so that a positive print of the photographic negative is obtained.

EXAMPLE 7 To a cellulose triacetate support provided with a subbing layer for gelatin a first layer is applied from the following composition pro rata of g/sq.m.:

l0 aqueous gelatin 900 ccs l0 aqueous saponin 30 ccs 5 aqueous solution of the condensation 30 ccs product of oleic acid and methyltaurine After drying, a second layer is applied thereto pro rata of 36 g/sq.m. from the following composition:

[0 aqueous gelatin 50 ccs 4O aqueous dispersion of poly(vinyl 80 ccs chloride) aqueous carbon dispersion as described in 4 ccs example 2 4 aqueous formaldehyde 2.5 ccs After drying, the material thus obtained is exposed together with an original, in thesame way as described in Example 2, but with an energy of 1 watt.sec./sq.cm. The material is then dipped in 5 percent aqueous solution of methylene blue so that a laterally reversed posi- 'tive print legible through the back of the support is obtained from the original Afterrinsing and drying, a stencil of the original is obtained.

EXAMPLE 6 A paper support weighing g/sq.m. provided with a 'baryta coating is covered pro rata of 36 g/sq.m. with a layer from the following composition:

l0 aqueous gelatin 150 g 40 dispersion of polyethylene as described in 80 g I example I l0 aqueousdispersion of colloidal silver 200 g EXAMPLE 8 To a cellulose triacetate support provided with a subbing layer for gelatin a first layer is applied pro rata of 15 g/sq.m. from the following composition:

l0 aqueous gelatin 400 g 5 aqueous saponin 30 g 5 aqueous solution of the condensation 30 g product of oleic acid and methyltaurine 4 aqueous formaldehyde 10 g l0 aqueous dispersion of colloidal silver 200 g After drying, a second layer is applied therto pro rata of 36 g/sq.m. from the following composition:

10 aqueous gelatin 50 g polyethylene dispersion as described in 80 g example 2 5 aqueous solution of sodium tetradecyl 40 g sulphate This materialis exposed as described in Example 6,

but with an energy of 0.9 watt.sec./sq.crn. Subsequently it is treated in the same way as described in Example 6 in order to produce a positive print.

EXAMPLE 9 A 7 percent aqueous solution of gelatin is applied in a proportion of 7 g of gelatin per sq.m. to a cellulose triacetate support. After drying the following composition is coated thereon in a proportion of 36 g/sq.m. and dried.

10 aqueous solution of gelatin 40 colloidal aqueous dispersion of 160 g polyethylene having a particle size less than 0.1 and an average molecular weight comprised between 15,000 and 30.000

water i 715 g 5 aqueous solution of sodium tetradecyl i 2 0 g sulphate Pigmentgruen B Colanyl Teig. (CI. 10006) 10 g the dye solution penetrates into the recording layer I only in the areas corresponding with the non-light reflecting image areas (black areas) and image areas which are coloured green (said image areas absorb blue and red), a laterally reversed blue copy (legible through the back of the support) of only the black and green letter marks of the original is obtained.

' When in the above described heat-sensitive layer the green pigment Pigmentgrun B Colanyl Teig (CI. 10006) is replaced by a same amount of Heliogenblau B Colanyl Teig(C.l. 74160) and the obtained material is exposed in above all the letter marks with exception of the red letter marks are reproduced. 7

When in the above described heat-sesntivie layer the green pigment Pigmentgrun B Colanyl Teig (C.l. 10006) is replaced by a same amount of Permanent Violett R.L. Colanyl Teig a 30 percent aqueous dispersion of Sirius lichtblau FF 2 GL.(C.l. 51300) and the obtained material is exposed as described above, a copy of the original showing the different letter marks in equal density of methylene blue absorbed is obtained.

When the exposed material containing Permanent Violett R.L. Colanyl Teig in the heat-sensitive layer thesame-way as described is braced on the printing cylinder of a planographic printing apparatus and inked thereon with an ink of the following composition:

aqueous carbon dispersion containing 53 g of 100 g carbon, 23 g of water, 18 g of glycol and 6 g nonylphenylpoly-cthylcne oxide aqueous solution of partly etherified melamine formaldehyde resin 20 g copoly(vinyl acetate/ammonium crotonate) 27 g /5 1,5 hexanediol 27 g 10 N ammonium hydroxide 2 g urea 2 g 53 aqueous dispersion of copoly (butyl 13 g aerylatc/vinyl acelate)50/50 white spirit (boiling range: l80-200C) 80 g xylene 20g I Only the areas corresponding with the iamge areas of the original are wetted with the aqueous coloured phase of the ink. I

By means of the planographic printing machine and the regular supply to the copying material of said ink, black prints are obtained from the original on common paper acting as receiving material.

EXAMPLE 10 A polyethylene terephthalate support of 0.1 mm thickness provided with a subbing layer for gelatin is coated with the following solution pro rata of 50 g/sq.m.

10% aqueous solution of gelatin 065 grams.

3% aqueous solution of the condensation product oi oleie 15 grams.

acid and methyltaurine.

10% aqueous solution of saponin 15 grams.

4% aqueous solution of formaldehyde 5 grams.

After solidifying a heat-sensitive layer is applied thereto from the following composition pro rate. of 36 g. per sq. m.

10% aqueous solution of gelatin 50 grams. 40% aqueous dispersion of polyethylene having a particle 80 grams.

size ot' less than 0.1 and an average molecular weight comprised between 15,000 and 30,000 7% aqueous solution otv ONa 128 grams.

Ira -Q0 Jim B 0 a 5% aqueous solution 01- S 03K S OzK 24 grams.

l N 0:0 KO-C ry aqueous solution of l l M t?OaNa ?O;Na' 124 grams.

N C=O H O-O N ll ll ll H3CC =CHC C-C H:

a? aqueous solution of sodium tetradecyl sulphate grams.

ater 200 grams.

' After dryingYIie EEt sEHsitivE materfiilisex posetm an original as described in Example I0. After exposure said material is slightly moistened with water and with its heat-sensitive layer pressed against a receiving paper as illustrated in FIG. 11. The heat-sensitive material 30 is led together with a receiving paper 36 between two pressure rollers 37 and 38 at a travelling speed of about 10 cm per see, the roller 38 being heated to 35C.

On emerging from the rollers the materials are immediately peeled apart, the receiving paper bearing a legible print of the original showing the different letter marks in equal density. I

EXAMPLE 1 1 To a cellulose triacetate support provided with a subbing layer for gelatin, a first layer is applied from the following composition pro rata of 30 g/sq.m.:

l0 aqueous gelatin 9 aqueous urea I70 l0 aqueous saponin 30 g 3 aqueous solution of the sodium salt of the g condensation product of oleic acid and mcthyltaurine Before coating this composition, its pH is adjusted to 4 with hydrogen chloride. After drying, a second layer is applied thereto from the following composition pro rata of g/sq.m.

l0 aqueous gelatin 50 g water 350 g aqueous emulsion of polyvinylidene 90 g chloride, prepared as described hereinafter 5 aqueous solution of sodium tetradecyl 25 g sulphate aqueous carbon dispersion as described in 4 g example 2 layer pressed against a blank planographic printing paper base, viz. a so-called GEVALITH (trade-name) paper composed of a paper support to which a baryta coating containing hardened gelatin has been applied as a binder at a ratio of g/sq.m.

The material and the printing paper are led between two pressure rollers at a travelling speed of about 10 cm/sec., both rollers being at room temperature. On emerging from between the rollers, both materials are peeled apart. The heat-sensitive layer is transferred image-wise to the receiving paper so as to form a legible print in accordance with the original.

The image-bearing printing plate thus obtained was exposed once more to a flash discharge and was braced onto a conventional offset printing machine and produced clear and sharp copies of the original.

PREPARATION OF POLY(VINYLIDENE CHLORIDE) LATEX In a heat-jacketed 800 ccs autoclave equipped with a stirrer, a thermometer, a manometer and an inlet for the reagents are placed successively liimirfiralized water 120 ccs. 10% solution of the sodium salt of the condensation product of oleic acid and methyltaurine in demineralized water (La. 2% by weight of monomer). 32 cos. 10% solution of the compound of the formula 160 ccs.

in demineralized water (Le. 10% by weight of monomer) 2% solution of potassium persulphate in demineralized 40 ccs.

water.- 5% sqlution of sodium hydrogen sulphate in demineralized 8 cos.

we er. Vinylidene chloride 160 grams.

The reaction mixture is heated to 60C with hot water whilst stirring at 1,000 rpm. After 30 minutes at this temperature, a pressure of 1.5 to 2 kg/sq.cm is attained in the autoclave. After a polymerisation time of 3 h at 60 C pr essure starts to drop and 2 l h later there A poly(ethylene terephthalate) support of 0.1 mm

. thickness provided with a subbing layer for gelatin is coated pro rata of 30 g/ sq.m. from the following composition:

tet radecylsulphate After" drying, the material is contact-exposed as schematically illustrated by FIG. 12 through a negative 

2. A method for reproducing an original according to claim 1, wherein said material is a finely divided dye or pigment which absorbs visible light in at least a portion of the whole visible spectrum.
 3. A method according to claim 1, wherein the exposure time is between 10 2 and 10 4 second.
 4. A method for reproducing information according to claim 1, wherein said layer is prepared starting from an aqueous dispersion of said thermoplastic polymer particles and said particles are used in a ratio greater than 3:2 by weight in respect of the hydrophilic binder.
 5. A method for reproducing an original according to claim 1, wherein the hydrophilic binder is a water-soluble colloid.
 6. A method for reproducing an original according to claim 5, wherein the said colloid is soluble in water at room temperature.
 7. A method for reproducing an original according to claim 5, wherein the hydrophilic binder is gelatin.
 8. A method for reproducing an original according to claim 6, wherein the said colloid is poly(N-vinylpyrrolidone).
 9. A method for reproducing an original according to claim 1, wherein the said hydrophobic polymer particles soften between 10* and 200*C above room temperature.
 10. A method for reproducing an original according to claim 1, wherein said polymer particles are sized from 0.1 Mu to 50 Mu .
 11. A method for reproducing an original according to claim 1, wherein the recording layer contains a wetting agent for the hydrophobic polymer. 